This invention concerns a cooling system for Direct Current electric arc furnaces.
The invention is applied for the cooling of the cathode, or electrode, in a Direct Current electric arc furnace used for the melting of metal alloys.
The cathodes in electric arc furnaces are at present composed of two main parts: a lower part made of graphite, from which the electric arc is sparked, and an upper part made of a metallic material, which also functions as a bearing element, associated with the electrode-bearing arm of the furnace.
These two parts are constrained together by means of an intermediate joint, normally threaded, made of an electroconductive material so as to allow the electric current to pass.
During the melting cycle, the graphite part reaches very high temperatures due to the electric arc, the passage of the electric currents used (Joule effect) and the heat exchange with the environment inside the furnace; the graphite part is thus progressively consumed, and is replaced by new segments of graphite from time to time. The high temperatures which can act on the graphite part cause the mechanical properties of the graphite to deteriorate, weakening the connection between the two parts of the cathode.
For this reason the cathode needs a cooling system which will act in correspondence with the metallic part and which is able to remove a large part of the heat which migrates from the graphite part towards the metallic part, allowing the desired temperature, both of the intermediate joint and of the metallic part, to be substantially controlled and maintained.
Some solutions include the use of traditional cooling systems with water, which however have not been considered satisfactory by operators in the field.